Summary of changes:

- Revamped the config/state system (CodaLabManager replaces config_parser).
- The BundleCLI and BundleRPCServer take the manager.
- Removed env_model; contents moved to state.json now.
- New entry point: cl.py, which includes both server and client.
- New syntax to switch client::worksheet: 'cl work dev::nlp'
- Support for aliases of addresses (including 'local').
- Ditched old config files; new ones are not compatible.
- Integrated prompting for password if trying to connect to remote server.